CA2071284C - Optical fiber and process of producing same - Google Patents
Optical fiber and process of producing sameInfo
- Publication number
- CA2071284C CA2071284C CA002071284A CA2071284A CA2071284C CA 2071284 C CA2071284 C CA 2071284C CA 002071284 A CA002071284 A CA 002071284A CA 2071284 A CA2071284 A CA 2071284A CA 2071284 C CA2071284 C CA 2071284C
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- Prior art keywords
- core portion
- core
- optical fiber
- fluorine
- refractive index
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C13/00—Fibre or filament compositions
- C03C13/04—Fibre optics, e.g. core and clad fibre compositions
- C03C13/045—Silica-containing oxide glass compositions
- C03C13/046—Multicomponent glass compositions
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/01413—Reactant delivery systems
- C03B37/0142—Reactant deposition burners
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
- C03B37/01—Manufacture of glass fibres or filaments
- C03B37/012—Manufacture of preforms for drawing fibres or filaments
- C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
- C03B37/01446—Thermal after-treatment of preforms, e.g. dehydrating, consolidating, sintering
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/02—Optical fibres with cladding with or without a coating
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
- C03B2201/12—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with fluorine
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/20—Doped silica-based glasses doped with non-metals other than boron or fluorine
- C03B2201/28—Doped silica-based glasses doped with non-metals other than boron or fluorine doped with phosphorus
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2201/00—Type of glass produced
- C03B2201/06—Doped silica-based glasses
- C03B2201/30—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi
- C03B2201/31—Doped silica-based glasses doped with metals, e.g. Ga, Sn, Sb, Pb or Bi doped with germanium
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2203/00—Fibre product details, e.g. structure, shape
- C03B2203/10—Internal structure or shape details
- C03B2203/22—Radial profile of refractive index, composition or softening point
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2203/00—Fibre product details, e.g. structure, shape
- C03B2203/10—Internal structure or shape details
- C03B2203/22—Radial profile of refractive index, composition or softening point
- C03B2203/24—Single mode [SM or monomode]
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2207/00—Glass deposition burners
- C03B2207/04—Multi-nested ports
- C03B2207/06—Concentric circular ports
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2207/00—Glass deposition burners
- C03B2207/20—Specific substances in specified ports, e.g. all gas flows specified
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B2207/00—Glass deposition burners
- C03B2207/50—Multiple burner arrangements
- C03B2207/54—Multiple burner arrangements combined with means for heating the deposit, e.g. non-deposition burner
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Optics & Photonics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- General Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Glass Compositions (AREA)
- Manufacture, Treatment Of Glass Fibers (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
- Glass Melting And Manufacturing (AREA)
- Surface Treatment Of Glass Fibres Or Filaments (AREA)
Abstract
In the optical fiber, the concentration of fluorine doped in the core portion is made nonuniform in the radial direction to be greater at the center portion of the core portion and less at the outer circumferential portion of the core portion. As a result, the distribution of the refractive index of the core portion and the cladding portion before the process of transparent glassification becomes a profile which is high at the outer circumferential portion of the core portion and which is low at the center portion. The reduction of the refractive index at the outer circumferential portion of the core portion due to the dispersion of the GeO2 etc., the oxide included in the core portion, in the cladding portion in the transparent glassification processed is and as a result, the profile of the refractive index of the core portion becomes one which sticks out in a step form with respect to the cladding portion.
Description
207128~
OPTICA~. FIBF.R AND PROCF.SS OF PRODUCING SAMF.
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to an oPtical fiber used, for example, in a long distance optical transmission sYstem, more particularly relates to an oPtical fiber preform and an optical fiber formed by the preform which improves the profile of the refractive index of the core Portion to an ideal shape and to a process of producing the same.
OPTICA~. FIBF.R AND PROCF.SS OF PRODUCING SAMF.
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates to an oPtical fiber used, for example, in a long distance optical transmission sYstem, more particularly relates to an oPtical fiber preform and an optical fiber formed by the preform which improves the profile of the refractive index of the core Portion to an ideal shape and to a process of producing the same.
2. Description of the Related Art For long distance optical transmission sYstems, single mode optical fibers with a core portion with an extremely reduced amount of doping of GeO2 by which the Rayleigh scattering coefficient is reduced, has been used. Usually fluorine is doped into a cladding portion of the fiber for the purpose of increasing the difference in refractive index with the core Portion.
In such a single mode optical fiber, the profile of the refractive index of the core portion desirably should have a step-like Profile compared with the cladding portion. This is in particular to Prevent an increase in the optical transmission loss with respect to bending of the optical fiber.
However, in the conventional optical fibers and processes of production thereof, it was not possible to make the profile *
of the refractive index of the core portion the ideal step shape.
As shown in Fig. 1, a core portion 2 ended up with a profile of the refractive index which sticks uP in a gentle mountain form compared with a cladding portion 4. Then, the optical fiber suffers from the problem that the effective refractive index of the core portion dropped and the optical transmission loss with respect to bending of the fiber increased.
Note that the reason why the profile of the refractive index as shown in Fig. l is obtained is considered to be because the GeO2 included in the core Portion vaPorizes from the surface of the soot during dehydration step and diffuses to the cladding portion at the interface of the core portion and cladding portion during the transparent glassification step in the Process of production of the oPtical fiber. Therefore, it is extremely difficult to dope GeO2 uniformly in the core portion and obtain a steP-like refractive index profile. Note that the dotted line portion A in Fig. 1 is a straight line corresPonding to the refractive index in the case of SiO2 alone without any dopins.
SUMMARY OF THE INVENTION
An obiect of the present invention is to provide an optical fiber preform and a process of producing the same which enables the Profile of the refractive index between a core portion and a cladding portion to be made the ideal profile and in Particular which enables the prevention of an increase in the optical transmission loss with respect to bending of an optical fiber.
According to the present invention there is provided an optical fiber preform including a core portion and a cladding portion provided on the outside of the core portion and having a refractive index smaller than the refractive index of the core portion, characterized in that at least the core portion is doped with fluorine and an oxide and in that the fluorine contained in the core Portion is doped more toward the center in the radial direction than the outer circumferential portion.
Preferably, the oxide is at least one of GeO2 and P2O5.
Also, preferably, the concentration of the GeO2 or P2O5 is up to 1 mol%.
Also, according to the present invention, there is Provided a process of producing an oPtical fiber preform characterized by forming a core Portion doped with an oxide and having a higher bulk density at the outer circumferential portion of the core portion compared with the center Portion and heat treating the core portion in a fluorine gas atmosPhere, thereby doPing the fluorine in the core portion so that the concentration of fluorine at the center portion of the core portion becomes relatively larger comPared with the outer circumferential portion.
Further, according to the present invention, there is Provided an oPtical fiber formed by the above optical fiber preform.
Also, according to the present invention, there is provided _ 4 a process for producing an optical fiber by using the above Process, and further including forming a cladding Portion provided on the outer circumference of the core portion so as to produce a fiber material, and transParent- glassifying the fiber material and drawing it so as to produce an optical fiber.
In the optical fiber of the present invention, the concentration of the fluorine doped in the core portion is made larger in the center portion of the core portion and made smaller in the outer circumferential portion of the core portion, so the Profile of the refractive index of the core Portion and the cladding portion before the step of transparent glassification becomes a profile which is high at the outer circumferential Portion of the core portion and which is low at the center portion. Therefore, the reduction of the refractive index at the outer circumferential Portion of the core portion due to the dispersion of the GeO2 etc., the oxide included in the core portion, in the cladding portion in the transparent glassification step is corrected and as a result, the Profile of the refractive index of the core portion becomes one which sticks out in a steP form with resPect to the cladding Portion.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other obiects and the above and other features of the present invention will be described in detail with reference to the accompanying drawings, in which, Figure 1 is a graph showing the Profile of the refractive 207128~
index of a conventional optical fiber preform, Figures 2a and 2b are graPhs showing the profile of the refractive index in the process of production of an optical fiber preform in accordance with an embodiment of the present invention, Figure 3 is a schematic view showing the process of production of an optical fiber preform according to an embodiment of the present invention, and Figure 4 is a graph showing the distribution of the bulk density of the core portion.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The optical fiber preform according to the Present invention has a core portion 2 comprised of silica based glass which is doped with an oxide and wherein the amount of the doping of fluorine is smaller at the outer circumferential portion comPared with the center Portion of the core portion. At the outer circumference of the core portion 2 a cladding portion 4 comprised of silica based glass with a lower refractive index compared with the core portion is provided. To lower the refractive index of the cladding Portion 4, the cladding portion 4 is doped uniformly with fluorine etc., for example.
The oxide to be doped in the core portion 2 is not particularly limited so long as it i5 an oxide where the refractive index of the core portion 2 is made higher comPared with the cladding Portion 4, but for example mention may be made of GeO2, P2O5, etc. The amount of doping of these oxides is preferably not more than 1 mol~ from the viewPoint of preventing optical loss due to Rayleigh scattering.
By making the amount of doping of the fluorine in the core portion 2 nonuniform and by reducing the amount of doping of the fluorine in the outer circumferential portion of the core portion 2 compared with the center portion, as shown in Fig. 2a, the profile of the refractive index of the core portion 2 and the cladding Portion 4 before the transParent glassification Process comes to have a profile higher at the outer circumferential portion of the core portion 2 and lower at the center Portion.
By doping the fluorine, the refractive index at that portion falls in accordance with the amount of doping. Therefore, the reduction in the refractive index at the outer circumferential portion of the core Portion 2 due to the dispersion of the GeO2 etc., serving as the oxide included in the core portion 2, in the cladding portion 4 in the process of transParent glassification is corrected. As a result, as shown in Fig. 2b, the profile of the refractive index of the core Portion 2 becomes a profile sticking out in a step form with resPect to the cladding portion 4.
The means for reducing the amount of fluorine doped at the outer circumferential Portion compared with the center portion of the core Portion 2 is not particularlY limited, but the following method may be considered.
When producing a core portion 2, the soot densitY is changed at the center Portion and the outer circumferential portion of the core portion 2 so as to make the soot density higher at the outer circumferential portion of the core portion 2 compared with the center Portion. After this, by the heat treatment under a fluorine gas atmosphere in the dehydration process or the transparent glassification Process, fluorine is doped so as to make the concentration higher at the center portion of the core portion 2. As a result, the profile of the refractive index of the core Portion 2 as shown in Fig. 2a is obtained.
The following method may be illustrated as a means for causing a change in the soot density of the core portion 2.
As shown in Fig. 3, when Producing a silica based glass particulate soot (preform) 10 for forming the core portion 2 by the VAD method, two burners 6 and 8 are used. A first burner 6 is directed to the lower tip portion of the soot for forming the core portion, and, is supplied with silicon chloride (SiCl4), germanium chloride (GeCl4), hydrogen gas (H2), oxygen gas(O2) and argon gas (Ar) and emits a flame including glass particles. A
second burner 8 is directed to the outer circumferential Portion of the soot 10 for sintering use, and, is supplied with hydrogen gas (H2) and oxygen gas (2) and emits a flame. By this VAD
method, the density of the Porous body comPrising the soot 10 becomes larger the more to the circumferential Portion of the core Portion 2. Therefore, regarding the density of the soot forming the core portion 2, the density at the outer circumferential Portion becomes larger than at the center Portion. Due to the heat treatment, including fluorine gas (F), at the subsequent processes, a core portion 2 is formed where more fluorine (F) is doPed the more to the center portion of the core portion 2.
Below, the present invention will be exPlained with reference to a more specific example, but the Present invention is not limited to this examPle.
F.x~m D le 1 By the method shown in Fig. 3, silica based glass particulate soot 10 for forming the core portion 2 is prepared.
Material gas such as shown in Table 1 is passed to silica based glass four-layer-tube burners 6 and 8. Note that in Table 1, the center tube of the four-layer-tube burner is made the first laYer and the surrounding tubes are successivelY made the second, third, and fourth layers.
207128~
g Table 1 First burner 6 Second burner 8 1st SiCl4(43 C) 115 [cc/min]
layer GeCl4(-3 C) 120 [cc/min]
2nd H2 5 9 [I/min] H2 5-9 [~/min]
layer 3rd Ar 1.7 [Ç/min] Ar 1.7 [~/min]
layer 4th 2 6.4 [Ç/min] 2 6.4 [~/min]
layer Investigating the densitY of the obtained soot 10 in the radial direction, as shown in Fig. 4, it was confirmed that the soot density of the porous body was larger the more to the outer circumferential portion of the core portion 2. Therefore, when doping fluorine under the conditions of Table 2, it is recognized that the fluorine is easier to dope the more to the center portion. The soot 10 was subiected to transparent glassification process under the conditions of Table 2 in a heating furnace (or electric furnace) for dehydration and transparent glassification.
-Table 2 1st step 2nd steP 3rd step Temperature ( C) 1100 900 1430 He flow rate 30 30 30 (Q/min) Cl2 flow rate 0.3 0.3 0.3 (Q/min) SiF4 flow rate 0 0.03 0 (Q/min) Falling rate 150 450 150 (mm/hr) This glass rod was drawn to a diameter of 10 mm, then silica based glass particulate was deposited on the outside of the silica based glass rod by the external dePosition method (OVD
method) and thereafter the process of transparent glassification under conditions of Table 3 in an electric furnace was repeated.
The deposition of silica based glass Particulates and the transparent glassification were performed until the cladding ratio of the core portion became 12.5. The resultant material was drawn at a rate of 180 m/min by a drawing furnace. An ultraviolet ray curing resin was immediately coated on it to give a sinsle mode oPtical fiber includins a core having a diameter of 10 ~m and a cladding having a 125 ~m, and a covering outer diameter of 250 ~m.
Table 3 1st step 2nd step Temperature ( C) 1000 1350 He flow rate (I/min) 30 15 Cl2 flow rate (I/min) 0.3 0.15 SiF4 flow rate (Q/min) 0 2.0 Falling rate (mm/hr) 450 150 ~Qm~arative Fxamvle 1 On the other hand, the same process as in Example 1 was used to PrePare a single mode optical fiber except that the core soot was prepared without using the four-layer-tube burner 2 in Fig.
In such a single mode optical fiber, the profile of the refractive index of the core portion desirably should have a step-like Profile compared with the cladding portion. This is in particular to Prevent an increase in the optical transmission loss with respect to bending of the optical fiber.
However, in the conventional optical fibers and processes of production thereof, it was not possible to make the profile *
of the refractive index of the core portion the ideal step shape.
As shown in Fig. 1, a core portion 2 ended up with a profile of the refractive index which sticks uP in a gentle mountain form compared with a cladding portion 4. Then, the optical fiber suffers from the problem that the effective refractive index of the core portion dropped and the optical transmission loss with respect to bending of the fiber increased.
Note that the reason why the profile of the refractive index as shown in Fig. l is obtained is considered to be because the GeO2 included in the core Portion vaPorizes from the surface of the soot during dehydration step and diffuses to the cladding portion at the interface of the core portion and cladding portion during the transparent glassification step in the Process of production of the oPtical fiber. Therefore, it is extremely difficult to dope GeO2 uniformly in the core portion and obtain a steP-like refractive index profile. Note that the dotted line portion A in Fig. 1 is a straight line corresPonding to the refractive index in the case of SiO2 alone without any dopins.
SUMMARY OF THE INVENTION
An obiect of the present invention is to provide an optical fiber preform and a process of producing the same which enables the Profile of the refractive index between a core portion and a cladding portion to be made the ideal profile and in Particular which enables the prevention of an increase in the optical transmission loss with respect to bending of an optical fiber.
According to the present invention there is provided an optical fiber preform including a core portion and a cladding portion provided on the outside of the core portion and having a refractive index smaller than the refractive index of the core portion, characterized in that at least the core portion is doped with fluorine and an oxide and in that the fluorine contained in the core Portion is doped more toward the center in the radial direction than the outer circumferential portion.
Preferably, the oxide is at least one of GeO2 and P2O5.
Also, preferably, the concentration of the GeO2 or P2O5 is up to 1 mol%.
Also, according to the present invention, there is Provided a process of producing an oPtical fiber preform characterized by forming a core Portion doped with an oxide and having a higher bulk density at the outer circumferential portion of the core portion compared with the center Portion and heat treating the core portion in a fluorine gas atmosPhere, thereby doPing the fluorine in the core portion so that the concentration of fluorine at the center portion of the core portion becomes relatively larger comPared with the outer circumferential portion.
Further, according to the present invention, there is Provided an oPtical fiber formed by the above optical fiber preform.
Also, according to the present invention, there is provided _ 4 a process for producing an optical fiber by using the above Process, and further including forming a cladding Portion provided on the outer circumference of the core portion so as to produce a fiber material, and transParent- glassifying the fiber material and drawing it so as to produce an optical fiber.
In the optical fiber of the present invention, the concentration of the fluorine doped in the core portion is made larger in the center portion of the core portion and made smaller in the outer circumferential portion of the core portion, so the Profile of the refractive index of the core Portion and the cladding portion before the step of transparent glassification becomes a profile which is high at the outer circumferential Portion of the core portion and which is low at the center portion. Therefore, the reduction of the refractive index at the outer circumferential Portion of the core portion due to the dispersion of the GeO2 etc., the oxide included in the core portion, in the cladding portion in the transparent glassification step is corrected and as a result, the Profile of the refractive index of the core portion becomes one which sticks out in a steP form with resPect to the cladding Portion.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other obiects and the above and other features of the present invention will be described in detail with reference to the accompanying drawings, in which, Figure 1 is a graph showing the Profile of the refractive 207128~
index of a conventional optical fiber preform, Figures 2a and 2b are graPhs showing the profile of the refractive index in the process of production of an optical fiber preform in accordance with an embodiment of the present invention, Figure 3 is a schematic view showing the process of production of an optical fiber preform according to an embodiment of the present invention, and Figure 4 is a graph showing the distribution of the bulk density of the core portion.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The optical fiber preform according to the Present invention has a core portion 2 comprised of silica based glass which is doped with an oxide and wherein the amount of the doping of fluorine is smaller at the outer circumferential portion comPared with the center Portion of the core portion. At the outer circumference of the core portion 2 a cladding portion 4 comprised of silica based glass with a lower refractive index compared with the core portion is provided. To lower the refractive index of the cladding Portion 4, the cladding portion 4 is doped uniformly with fluorine etc., for example.
The oxide to be doped in the core portion 2 is not particularly limited so long as it i5 an oxide where the refractive index of the core portion 2 is made higher comPared with the cladding Portion 4, but for example mention may be made of GeO2, P2O5, etc. The amount of doping of these oxides is preferably not more than 1 mol~ from the viewPoint of preventing optical loss due to Rayleigh scattering.
By making the amount of doping of the fluorine in the core portion 2 nonuniform and by reducing the amount of doping of the fluorine in the outer circumferential portion of the core portion 2 compared with the center portion, as shown in Fig. 2a, the profile of the refractive index of the core portion 2 and the cladding Portion 4 before the transParent glassification Process comes to have a profile higher at the outer circumferential portion of the core portion 2 and lower at the center Portion.
By doping the fluorine, the refractive index at that portion falls in accordance with the amount of doping. Therefore, the reduction in the refractive index at the outer circumferential portion of the core Portion 2 due to the dispersion of the GeO2 etc., serving as the oxide included in the core portion 2, in the cladding portion 4 in the process of transParent glassification is corrected. As a result, as shown in Fig. 2b, the profile of the refractive index of the core Portion 2 becomes a profile sticking out in a step form with resPect to the cladding portion 4.
The means for reducing the amount of fluorine doped at the outer circumferential Portion compared with the center portion of the core Portion 2 is not particularlY limited, but the following method may be considered.
When producing a core portion 2, the soot densitY is changed at the center Portion and the outer circumferential portion of the core portion 2 so as to make the soot density higher at the outer circumferential portion of the core portion 2 compared with the center Portion. After this, by the heat treatment under a fluorine gas atmosphere in the dehydration process or the transparent glassification Process, fluorine is doped so as to make the concentration higher at the center portion of the core portion 2. As a result, the profile of the refractive index of the core Portion 2 as shown in Fig. 2a is obtained.
The following method may be illustrated as a means for causing a change in the soot density of the core portion 2.
As shown in Fig. 3, when Producing a silica based glass particulate soot (preform) 10 for forming the core portion 2 by the VAD method, two burners 6 and 8 are used. A first burner 6 is directed to the lower tip portion of the soot for forming the core portion, and, is supplied with silicon chloride (SiCl4), germanium chloride (GeCl4), hydrogen gas (H2), oxygen gas(O2) and argon gas (Ar) and emits a flame including glass particles. A
second burner 8 is directed to the outer circumferential Portion of the soot 10 for sintering use, and, is supplied with hydrogen gas (H2) and oxygen gas (2) and emits a flame. By this VAD
method, the density of the Porous body comPrising the soot 10 becomes larger the more to the circumferential Portion of the core Portion 2. Therefore, regarding the density of the soot forming the core portion 2, the density at the outer circumferential Portion becomes larger than at the center Portion. Due to the heat treatment, including fluorine gas (F), at the subsequent processes, a core portion 2 is formed where more fluorine (F) is doPed the more to the center portion of the core portion 2.
Below, the present invention will be exPlained with reference to a more specific example, but the Present invention is not limited to this examPle.
F.x~m D le 1 By the method shown in Fig. 3, silica based glass particulate soot 10 for forming the core portion 2 is prepared.
Material gas such as shown in Table 1 is passed to silica based glass four-layer-tube burners 6 and 8. Note that in Table 1, the center tube of the four-layer-tube burner is made the first laYer and the surrounding tubes are successivelY made the second, third, and fourth layers.
207128~
g Table 1 First burner 6 Second burner 8 1st SiCl4(43 C) 115 [cc/min]
layer GeCl4(-3 C) 120 [cc/min]
2nd H2 5 9 [I/min] H2 5-9 [~/min]
layer 3rd Ar 1.7 [Ç/min] Ar 1.7 [~/min]
layer 4th 2 6.4 [Ç/min] 2 6.4 [~/min]
layer Investigating the densitY of the obtained soot 10 in the radial direction, as shown in Fig. 4, it was confirmed that the soot density of the porous body was larger the more to the outer circumferential portion of the core portion 2. Therefore, when doping fluorine under the conditions of Table 2, it is recognized that the fluorine is easier to dope the more to the center portion. The soot 10 was subiected to transparent glassification process under the conditions of Table 2 in a heating furnace (or electric furnace) for dehydration and transparent glassification.
-Table 2 1st step 2nd steP 3rd step Temperature ( C) 1100 900 1430 He flow rate 30 30 30 (Q/min) Cl2 flow rate 0.3 0.3 0.3 (Q/min) SiF4 flow rate 0 0.03 0 (Q/min) Falling rate 150 450 150 (mm/hr) This glass rod was drawn to a diameter of 10 mm, then silica based glass particulate was deposited on the outside of the silica based glass rod by the external dePosition method (OVD
method) and thereafter the process of transparent glassification under conditions of Table 3 in an electric furnace was repeated.
The deposition of silica based glass Particulates and the transparent glassification were performed until the cladding ratio of the core portion became 12.5. The resultant material was drawn at a rate of 180 m/min by a drawing furnace. An ultraviolet ray curing resin was immediately coated on it to give a sinsle mode oPtical fiber includins a core having a diameter of 10 ~m and a cladding having a 125 ~m, and a covering outer diameter of 250 ~m.
Table 3 1st step 2nd step Temperature ( C) 1000 1350 He flow rate (I/min) 30 15 Cl2 flow rate (I/min) 0.3 0.15 SiF4 flow rate (Q/min) 0 2.0 Falling rate (mm/hr) 450 150 ~Qm~arative Fxamvle 1 On the other hand, the same process as in Example 1 was used to PrePare a single mode optical fiber except that the core soot was prepared without using the four-layer-tube burner 2 in Fig.
3.
The two single mode fibers were wound on a 15 mm~ and 20 mm~
mandrel and compared as to the increase in loss due to bending.
The results are shown in Table 4.
--Table 4 Single mode Increase in loss ~c (~m) ~ t%) oPtical fiber (dB/km) 15 mm~ 20 mm~
Example 1 1.1 0.1 1.47 0.36 Profile of refractive index shown in Fig.
l(B) Comp. Ex. 1 4.0 0.4 1.47 0.35 Profile of refractive index shown in Fig. 4 As shown in Table 4, Example 1 was confirmed to have a smaller increase in loss with respect to bending compared with the conventional optical fiber shown in Comparative Example 1.
Note that in the above-mentioned embodiment, an examPle of a single-mode optical fiber was shown, but the present invention may be aPPlied to a multiPle-mode optical fiber and a constant polarized light optical fiber as well. Further, the core maY be doped with P2O5 instead of GeO2. However, if too much is doPed, the optical loss due to RaYleigh scattering becomes significant.
Therefore, it is preferable that the concentration of the GeO2 207128~
or the P205 be made not more than 1 mol%.
As explained above, according to the Present invention, there is provided an optical fiber doped with a small amount of an oxide at the core which has the superior effects of enabling the distribution of the refractive index of the core portion and the cladding Portion to be made the ideal profile and enabling a reduction of the optical transmission loss with respect to bending of the optical fiber.
Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention, and it should be understood that the present invention is not restricted to the specific embodiments described above.
The two single mode fibers were wound on a 15 mm~ and 20 mm~
mandrel and compared as to the increase in loss due to bending.
The results are shown in Table 4.
--Table 4 Single mode Increase in loss ~c (~m) ~ t%) oPtical fiber (dB/km) 15 mm~ 20 mm~
Example 1 1.1 0.1 1.47 0.36 Profile of refractive index shown in Fig.
l(B) Comp. Ex. 1 4.0 0.4 1.47 0.35 Profile of refractive index shown in Fig. 4 As shown in Table 4, Example 1 was confirmed to have a smaller increase in loss with respect to bending compared with the conventional optical fiber shown in Comparative Example 1.
Note that in the above-mentioned embodiment, an examPle of a single-mode optical fiber was shown, but the present invention may be aPPlied to a multiPle-mode optical fiber and a constant polarized light optical fiber as well. Further, the core maY be doped with P2O5 instead of GeO2. However, if too much is doPed, the optical loss due to RaYleigh scattering becomes significant.
Therefore, it is preferable that the concentration of the GeO2 207128~
or the P205 be made not more than 1 mol%.
As explained above, according to the Present invention, there is provided an optical fiber doped with a small amount of an oxide at the core which has the superior effects of enabling the distribution of the refractive index of the core portion and the cladding Portion to be made the ideal profile and enabling a reduction of the optical transmission loss with respect to bending of the optical fiber.
Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention, and it should be understood that the present invention is not restricted to the specific embodiments described above.
Claims (8)
1. An optical fiber preform including a core portion and a cladding portion provided on the outside of the core portion and having a refractive index smaller than the refractive index of the core portion, said optical fiber preform characterized in that at least the core portion is doped with fluorine and an oxide and in that the fluorine contained in the core portion is doped more toward the center in the radial direction than the outer circumferential portion.
2. An optical fiber preform as set forth in claim 1, wherein the oxide is at least one of GeO2 and P2O5.
3. An optical fiber preform as set forth in claim 2, wherein characterized in that the concentration of the GeO2 or P2O5 is up to 1 mol%.
4. A process of producing an optical fiber preform characterized by forming a core portion doped with an oxide and having a higher soot density at the outer circumferential portion of the core portion compared with the center portion and heat treating the core portion in a fluorine gas atmosphere, thereby doping the fluorine in the core portion so that the concentration of fluorine at the center portion of the core portion becomes relatively larger compared with the outer circumferential portion.
5. An optical fiber including a core and a cladding provided on the outside of the core and having a refractive index smaller than the refractive index of the core, said optical fiber characterized in that at least the core portion is doped with fluorine and an oxide and in that the fluorine contained in the core is doped more toward the center in the radial direction than the outer circumferential portion.
6. An optical fiber as set forth in claim 1, wherein the oxide is at least one of GeO2 and P2O5.
7. An optical fiber as set forth in claim 2, wherein characterized in that the concentration of the GeO2 or P2O5 is up to 1 mol%.
8. A process of producing an optical fiber characterized by forming a core doped with an oxide and having a higher bulk density at the outer circumferential portion of the core compared with the center portion and heat treating the core portion in a fluorine gas atmosphere, thereby doping the fluorine in the core portion so that the concentration of fluorine at the center portion of the core portion becomes relatively larger compared with the outer circumferential portion, forming a cladding portion provided on the outer circumference of the core portion so as to produce a fiber material, and transparent- glassifying the fiber material and drawing it so as to produce an optical fiber including a core formed by said core portion and a cladding formed by said cladding portion.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP3178705A JP2959877B2 (en) | 1991-06-24 | 1991-06-24 | Optical fiber manufacturing method |
JP3-178,705 | 1991-06-24 |
Publications (2)
Publication Number | Publication Date |
---|---|
CA2071284A1 CA2071284A1 (en) | 1992-12-25 |
CA2071284C true CA2071284C (en) | 1996-11-12 |
Family
ID=16053122
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002071284A Expired - Fee Related CA2071284C (en) | 1991-06-24 | 1992-06-15 | Optical fiber and process of producing same |
Country Status (6)
Country | Link |
---|---|
US (1) | US5210816A (en) |
EP (1) | EP0520337B1 (en) |
JP (1) | JP2959877B2 (en) |
AU (1) | AU646572B2 (en) |
CA (1) | CA2071284C (en) |
DE (1) | DE69204377D1 (en) |
Families Citing this family (22)
Publication number | Priority date | Publication date | Assignee | Title |
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US5278931A (en) * | 1992-12-31 | 1994-01-11 | Corning Incorporated | Low bend loss singlemode optical waveguide fiber |
US5509101A (en) * | 1994-07-11 | 1996-04-16 | Corning Incorporated | Radiation resistant optical waveguide fiber and method of making same |
US5613027A (en) * | 1994-10-17 | 1997-03-18 | Corning Incorporated | Dispersion shifted optical waveguide fiber |
US6018533A (en) * | 1995-04-21 | 2000-01-25 | Ceramoptec Industries, Inc. | Optical fiber and integrated optic lasers with enhanced output power |
JP3457848B2 (en) * | 1997-06-19 | 2003-10-20 | 京セラ株式会社 | Manufacturing method of optical waveguide |
JP3470016B2 (en) * | 1997-07-31 | 2003-11-25 | 京セラ株式会社 | Method of manufacturing optical integrated circuit board |
US6556756B2 (en) | 1999-03-17 | 2003-04-29 | Corning Incorporated | Dispersion shifted optical waveguide fiber |
US6263706B1 (en) * | 1999-03-30 | 2001-07-24 | Deliso Evelyn M. | Method of controlling fluorine doping in soot preforms |
DE10027263B4 (en) * | 2000-05-31 | 2011-11-24 | Jenoptik Laser Gmbh | A method of making an SiO2-based optical fiber for transmitting a high power density |
JP3865039B2 (en) * | 2000-08-18 | 2007-01-10 | 信越化学工業株式会社 | Method for producing synthetic quartz glass, synthetic quartz glass and synthetic quartz glass substrate |
US6915665B2 (en) * | 2000-10-31 | 2005-07-12 | Corning Incorporated | Method of inducing transmission in optical lithography preforms |
US6715322B2 (en) * | 2001-01-05 | 2004-04-06 | Lucent Technologies Inc. | Manufacture of depressed index optical fibers |
US6853798B1 (en) * | 2001-10-15 | 2005-02-08 | Sandia Corporation | Downhole geothermal well sensors comprising a hydrogen-resistant optical fiber |
JP2004149371A (en) * | 2002-10-31 | 2004-05-27 | Fujikura Ltd | Method for manufacturing fluorine added glass material and fluorine added glass material |
WO2005051854A1 (en) * | 2003-11-29 | 2005-06-09 | Optomagic Co.Ltd | Manufacturing method for single mode optical fiber |
EP1806599A4 (en) * | 2004-10-22 | 2010-09-22 | Fujikura Ltd | Optical fiber, transmission system and multiple wavelength transmission system |
JP5779606B2 (en) * | 2013-03-14 | 2015-09-16 | 株式会社フジクラ | Amplifying optical fiber and fiber laser device using the same |
JP6513796B2 (en) * | 2014-09-16 | 2019-05-15 | コーニング インコーポレイテッド | Method of making an optical fiber preform having a one-step fluorine trench and overcladding |
WO2017080564A1 (en) | 2015-11-10 | 2017-05-18 | Nkt Photonics A/S | An element for a preform, a fiber production method and an optical fiber drawn from the preform |
JP7107840B2 (en) | 2015-12-23 | 2022-07-27 | エヌケイティー フォトニクス アクティーゼルスカブ | Hollow core optical fiber and laser system |
CN108474914B (en) | 2015-12-23 | 2021-02-02 | Nkt光子学有限公司 | Photonic crystal fiber assembly |
US10663326B2 (en) * | 2017-08-21 | 2020-05-26 | Corning Incorporated | Rayleigh scattering based distributed fiber sensors with optimized scattering coefficients |
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US4082420A (en) * | 1972-11-25 | 1978-04-04 | Sumitomo Electric Industries, Ltd. | An optical transmission fiber containing fluorine |
US3981707A (en) * | 1975-04-23 | 1976-09-21 | Corning Glass Works | Method of making fluorine out-diffused optical device |
US4210386A (en) * | 1975-04-23 | 1980-07-01 | Corning Glass Works | Fluorine out-diffused optical device and method |
US4339173A (en) * | 1975-09-08 | 1982-07-13 | Corning Glass Works | Optical waveguide containing P2 O5 and GeO2 |
FR2432478B1 (en) * | 1978-07-31 | 1982-03-12 | Quartz & Silice | |
US4413882A (en) * | 1980-07-03 | 1983-11-08 | Corning Glass Works | Low viscosity core glass optical fiber |
GB2100464B (en) * | 1981-05-11 | 1985-07-17 | Bicc Plc | An improved optical fibre |
US4616901A (en) * | 1982-04-09 | 1986-10-14 | At&T Bell Laboratories | Doped optical fiber |
GB2129152B (en) * | 1982-10-30 | 1986-08-13 | Standard Telephones Cables Ltd | Optical fibres |
JPS60215550A (en) * | 1984-04-12 | 1985-10-28 | Sumitomo Electric Ind Ltd | Quartz based glass fiber for optical transmission containing fluorine and p2o5 |
DE3500672A1 (en) * | 1985-01-11 | 1986-07-17 | Philips Patentverwaltung | LIGHT-GUIDE FIBER WITH FLUOROUS DOPING AND METHOD FOR THE PRODUCTION THEREOF |
JPS61191543A (en) * | 1985-02-15 | 1986-08-26 | Furukawa Electric Co Ltd:The | Quartz base optical fiber |
JPS62108744A (en) * | 1985-11-06 | 1987-05-20 | Furukawa Electric Co Ltd:The | Transparent vitrification method of porous glass base material |
JP2557388B2 (en) * | 1987-06-02 | 1996-11-27 | キヤノン株式会社 | Gradient index type optical element and manufacturing method thereof |
JPH0717395B2 (en) * | 1987-07-20 | 1995-03-01 | 住友電気工業株式会社 | Manufacturing method of base material for dispersion shift fiber |
GB8724736D0 (en) * | 1987-10-22 | 1987-11-25 | British Telecomm | Optical fibre |
US5048923A (en) * | 1989-04-07 | 1991-09-17 | Fujikura, Ltd. | Image fiber, image fiber preform, and manufacturing processes thereof |
JPH02285305A (en) * | 1989-04-27 | 1990-11-22 | Fujikura Ltd | Fiber for laser light transmission and production thereof |
-
1991
- 1991-06-24 JP JP3178705A patent/JP2959877B2/en not_active Expired - Lifetime
-
1992
- 1992-06-15 CA CA002071284A patent/CA2071284C/en not_active Expired - Fee Related
- 1992-06-16 AU AU18271/92A patent/AU646572B2/en not_active Ceased
- 1992-06-17 US US07/899,864 patent/US5210816A/en not_active Expired - Fee Related
- 1992-06-19 DE DE69204377T patent/DE69204377D1/en not_active Expired - Lifetime
- 1992-06-19 EP EP92110392A patent/EP0520337B1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
AU1827192A (en) | 1993-01-07 |
JPH052118A (en) | 1993-01-08 |
JP2959877B2 (en) | 1999-10-06 |
EP0520337A1 (en) | 1992-12-30 |
DE69204377D1 (en) | 1995-10-05 |
CA2071284A1 (en) | 1992-12-25 |
US5210816A (en) | 1993-05-11 |
AU646572B2 (en) | 1994-02-24 |
EP0520337B1 (en) | 1995-08-30 |
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